In an active matrix liquid crystal display device, a plurality of scanning lines and a plurality of signal lines are provided in one substrate. A display pixel is provided at each of intersection points of the signal lines and the scanning lines. Each of the display pixels includes a switching element and can individually apply an electric potential to a liquid crystal. A surrounding area (frame portion) which does not include the display pixel is arranged around the display area which includes each of the display pixels. An opposed substrate includes a black matrix in order to prevent transmission of a backlight (light leakage) in the frame portion.
In order to reduce a production cost of the above-mentioned liquid crystal display device, it is effective to eliminate the black matrix provided on the opposed substrate. For that purpose, a laminated pattern including color layers is provided in the frame portion to function as a light shielding layer. However, light shielding ability of the light shielding layer that is formed by using the laminated pattern including color layers is insufficient. Therefore, in a liquid crystal display device of a normally white mode using a TN (Twisted Nematic) system, the frame portion may be colored. As a result, sufficient display quality can not be obtained.
To solve the problem above described, Japanese Patent Registration No. 3327508 (patent document 1) discloses a liquid crystal display device having a structure in which a light shielding layer composed of an opaque electrode 16 covers a gap between scanning lines or a gap between signal lines (in FIG. 16, a gap between signal lines) that is arranged in a surrounding area (frame portion) as shown in FIG. 16. Japanese Patent Application Laid-Open No. 1997-73101 discloses a liquid crystal display device having a structure in which a transparent electrode is arranged in an upper layer of an opaque electrode in order to improve transmissivity of a liquid crystal panel and reduce light reflection from a display surface.
In recent years, a liquid crystal display device of a normally black mode such as an IPS (In-Plane Switching) system has been developed as a display device having a wide view angle display. In the display device, black is displayed in an area where an electric field is not formed between wiring lines although a light shielding layer does not exist in the area. Therefore, the above-mentioned liquid crystal display device can maintain sufficient display quality by using only a light shielding layer made of laminated color layers. However, an electric field is generated between the wiring lines in a place at which two kinds of wiring lines that have a different electric potential from each other cross. As a result, a light transmits through only the portion. Therefore, a light leakage with a specific pattern occurs at the frame portion disadvantageously.
An intersection of wiring lines each having a different electric potential is necessarily required when a protection transistor in order to prevent electrostatic breakdown of a switching element is arranged or wiring lines are laid in the surrounding area (frame portion).
For example, as shown in FIG. 17, in the frame portion around the display area, when a common electrode 3 is arranged on a portion in which a plurality of scanning lines 2 are provided, a strong electric field is generated at an intersection portion between the scanning line 2 and the common electrode 3 as indicated by arrows shown in FIG. 17. As shown in FIG. 18 which shows a cross-sectional structure along a line F1-F2 in FIG. 17, the strong electric field penetrates a liquid crystal layer 10. Therefore, a liquid crystal rotates and causes light leakage.
The light leakage can be avoided by providing a light shielding layer composed of an opaque electrode 16 as shown in the patent document 1 (FIG. 16). However, two wiring lines are stacked at the intersectional portion. When the light shielding layer composed of the opaque electrode is added at the portion in addition to the stacked wiring lines, manufacturing processes increase.